[meteorite-list] Mars Exploration Rover Update - November 18, 2004

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Nov 18 16:33:27 2004
Message-ID: <200411182107.NAA07970_at_zagami.jpl.nasa.gov>

http://marsrovers.jpl.nasa.gov/mission/status.html

SPIRIT UPDATE: Three hundred sols and counting! - sol 292-305,
November 18, 2004

Spirit remains in excellent health and has survived more than 300
martian days on the red planet.

With the Sun still relatively low on the horizon in the early spring
season on Mars, rover drivers are forced to seek driving routes that
keep the rover and its solar panels tilted northward for energy reasons.
That constraint, plus the rocky terrain, will challenge rover drivers in
the coming weeks.

Over the last few weeks, the electrical "brakes" on Spirit's right-front
and left-rear steering actuators (motors) apparently failed to disengage
during drive attempts. The most likely cause of this anomaly is the
buildup of insulating material on the electronic relay contacts that
indicate that the brakes are disengaged. To help ensure successful
future drives, engineers decided to permanently ignore the
"brake-disengaged" indicator. If their theory is correct, the brake will
actually be disengaged despite the "failure-to-disengage" indication. If
they are wrong, a fuse in the brake circuit will safely blow when they
attempt to move the steering actuators. In either case, driving
operations will not be adversely affected.

A few sols ago, Spirit's engineering team discovered an electric-circuit
grounding problem between the rover chassis and the power bus return.
This incident occurred at the exact time the Spirit team was performing
an inspection of the instrument deployment device, or robotic arm. The
inspection sequence commanded one of the arm joints to a position beyond
where it had previously been. That particular joint, joint number 5, is
the rover arm turret, which rotates the four rover arm instruments into
position. This coincidence may indicate that the joint 5 move somehow
created the electrical short; it could also just be coincidence. The
mechanical team has not found any reason to suspect a failure in the
joint 5 cabling. To be safe, the engineering team has constrained the
use of joint 5 on Spirit and Opportunity to avoid this extreme position.
The constraint is not expected to significantly impact normal
operations. The apparent short may also be the result of a failed
measurement circuit. The short, if real, has no immediate effect on the
rover, but does remove one layer of protection against effects of future
shorts should they occur.

Between sols 292 and 298, Spirit completed its studies of the rock
called "Uchben" and drove west about 2 meters (almost 7 feet) to a rock
called "Lutefisk."

Between sols 299-303, Spirit finished its investigation of Lutefisk.
Lutefisk, a rock with some interesting nodules, lies a site roughly 40
meters (131 feet) above and 2700 meters (1.67 miles) away from Spirit's
landing site on the Gusev plain. Team members should know more about the
chemistry of Lutefisk and its nodules when they receive results from the
alpha particle X-ray spectrometer and Mossbauer spectrometer.

For coming sols, Spirit is in an exploration and discovery mode,
continuing the rover's ascent towards "Machu Picchu" in the Columbia
Hills. Spirit will stop at interesting rocks along the way.
Received on Thu 18 Nov 2004 04:07:04 PM PST